Annular cutter with exchangeable bit ring

ABSTRACT

A core drill is arranged to drill in the ground, the core drill having a sleeve with a first end portion and a bit ring which is detachably attached in a rotationally rigid manner to the first end portion, one of the sleeve and the bit ring having a groove with two converging side faces, and the other one of the sleeve and the groove having a protrusion with two complementary side faces, and the groove and the protrusion being arranged to engage with each other.

The invention relates to an annular cutter arranged to drill in the ground, the annular cutter including an exchangeable bit ring. The invention also relates to an assembly comprising an annular cutter and a drive unit, the annular cutter being connected to the drive unit.

BACKGROUND OF THE INVENTION

When forming larger holes or slots, it is known to use annular cutters, also referred to as hole saws, core cutters or core-barrel drills. The annular cutter is provided, at a first end portion, with several teeth and is connected, at a second end portion, to a drive unit. Produced in a typical way, the teeth are made from a relatively hard material, for example diamond or tungsten carbide.

The teeth may be attached by welding, so-called hard-soldering in which a binder containing silver is used, using a curable fastening means, screw connections or by wedging the teeth. The teeth may be round or flat, and they may have a directionally specific or a directionally neutral direction of motion. A tooth with a directionally neutral direction of motion typically has a symmetric design.

Annular cutters arranged to be used in the ground are typically provided with detachable teeth. Because the teeth are attached and detached individually, changing teeth is a time-consuming and expensive operation. It is also known that the annular cutter may have to be detached from the drive unit when teeth are to be changed. If the change of teeth includes soldering and curable fastening means, time must be added for curing before the annular cutter can be put into operation again.

In core-drilling in mountains and rugged terrain, it is common to use a helicopter to transport the annular cutter and associated equipment and crew. When the lifting operation has been carried out, the helicopter generally stands waiting on the ground nearby, waiting to move the equipment and the crew to the next drilling operation. It is therefore important that the drilling operations and associated maintenance can be carried out as efficiently as possible. Changing teeth outside planned maintenance intervals may involve the drilling operation coming to a halt, and both crew and other equipment may become idle. Causes of such interruptions may be extra great wear or damage to the teeth. In order to reduce the stoppage at a change of teeth, the industry is in search of alternative and simpler solutions.

Annular cutters adapted for drilling in concrete, for example a concrete wall, are known, the annular cutter including a sleeve and a detachable bit ring. The bit ring is provided with a plurality of T-shaped recesses which have their mouths in the first end portion of the bit ring, and the sleeve is provided, in its first end portion, with corresponding locking pins arranged radially. The bit ring may be locked axially to the sleeve by the bit ring being pushed onto the sleeve in such a way that the locking pins reach the bottom of the T-shaped recesses and then being turned clockwise or counter-clockwise. The solution has several drawbacks:

-   -   The bit ring may come loose and fall off the sleeve if the         direction of rotation of the annular cutter changes direction         while the annular cutter is simultaneously being pulled out of         the sleeve, or if the bit ring has got displaced on the sleeve.     -   The first end portion of the bit ring is divided and may thereby         easily be subject to breakage and structural weakening,         especially if the material being drilled includes loose         particles, for example grit and stones.     -   The locking pins are unprotected and thereby subject to wear and         damage, especially if the material being drilled includes loose         particles, for example grit and stones.

GENERAL DESCRIPTION OF THE INVENTION

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect, the invention relates to an annular cutter arranged to drill in the ground, the annular cutter comprising a sleeve with a first end portion and a bit ring which is detachably attached in a rotationally rigid manner to the first end portion. One of the sleeve and the bit ring has a groove with two converging side faces and the other one of the sleeve and the bit ring has a protrusion with two complementary side faces, and the groove and the protrusion are arranged to engage with each other.

The effect of the groove and the recess having two converging and complementary side faces is that a conical coupling portion is formed, in which the bit ring is wedged to the sleeve so that a greater torque may be transmitted from the sleeve to the bit ring than in a coupling portion with a flat contact surface. The angle may typically be 10° to a centre axis of the annular cutter. The angle may be smaller than 10°. The angle may be larger than 10°. When a small angle is used between the sleeve and the bit ring, a greater torque may be transmitted than when a large angle is used.

Advantageously, the groove and the protrusion may be formed with, respectively, a flat bottom and a flat end so that it is only the converging side faces that are in contact with each other, in order thereby to create a largest possible friction surface between the bit ring and the sleeve.

At least one side face may be provided with a friction-promoting surface. The friction-promoting surface may be a friction coating. The friction-promoting surface may be formed by working the sloping surface, for example a mechanical processing in which an uneven surface in the form of flutes or grooves is formed.

The effect of the rotationally rigid attachment according to the invention is that it is possible to transmit rotary motion of alternating directions from the sleeve to the bit ring without any relative motion between the sleeve and the bit ring arising. Thereby it is possible to change the direction of rotation of the annular cutter without undue wear arising, and to change the direction of rotation while the annular cutter is simultaneously being pulled out of the slot in the ground without a risk of the bit ring coming loose from the sleeve. A rotary motion of alternating directions may be necessary to release a wedged drill, or if it is necessary to pull the annular cutter out to clean the slot of drilling dust and particles. This makes the annular cutter particularly suited for drilling in the ground, for example in a mountain and/or a rock.

Further, the invention makes it possible to combine a rotationally rigid attachment of the bit ring with a simultaneous replacement of all the teeth. The teeth replacement may thereby be done more quickly and more cost-effectively than today. By changing the direction of rotation, it is also possible to have a more even wear on the teeth, if directionally neutral teeth are used. The bit ring and the sleeve may include a radial contact surface and/or an axial contact surface.

The bit ring may be detachably attached to the sleeve via a coupling arranged to absorb an axial force which is greater than an axial lifting force necessary for lifting the annular cutter out of the ground. The coupling is placed between the first end portion of the sleeve and the bit ring. By the coupling being stronger than the lifting force, as described by the invention, the risk of the bit ring falling off or being pulled off the sleeve in a possible releasing of a wedged bit ring, or in a withdrawal of the annular cutter where a portion of the ground has come loose and is resting against the bit ring and/or the teeth, is reduced or removed. This problem is particularly great in drilling in porous rock, where a portion of the rock may come loose and wedge the annular cutter.

The coupling may include fastening means taken from a group including screws, clamping sleeves and wedges. A coupling including said fastening means may give simple and quick attaching and detaching of the bit ring by the use of only simple hand-held tools. A screw connection makes it possible to attach the bit ring with a desired torque against the sleeve, and the screw connection may absorb both axial and radial forces. The screw may advantageously include an internal engagement portion for a tool, to protect the engagement portion from wear and damage. Such screws are known as, for example, Allen and Torx. A clamping sleeve is arranged to absorb radial forces and has the advantage of enabling quick and simple attachment and detachment by the use of an impact tool.

During drilling in the ground, a screw, sleeve or wedge as described herein will be subjected to shear forces, as a torque is created between the bit ring and the sleeve. These shear forces may be reduced if the bit ring is arranged on the first end portion via a conical coupling portion according to the invention.

Long-time testing performed by the applicant shows that the conical coupling portion gives a substantial reduction in vibrations and especially so-called chatter, which is vibrations that may arise when long drills are used. The conical coupling portion means that the axial drilling force may be increased, so that the progress in the drilling can be increased as well. The cause of this favourable effect is assumed to be the wedge effect that is achieved at the conical coupling portion and the fact that the conical coupling portion between the sleeve and the bit ring gives a more rigid coupling than alternative solutions.

The fastening means may be arranged at the end portion of the sleeve. The sleeve may have a thickness enabling the arrangement of an axial threaded portion for a screw suitable for screwing the bit ring to the sleeve. The bit ring may advantageously have a thickness that is equal to or larger than the diameter of said screw, in order thereby to give the screw radial protection during drilling. The bit ring may include a recess or cut-out arranged to protect the screw during drilling. The cut-out may be open or closed. An open cut-out enables the use of an axial tightening tool, for example a straight screw-driver or a screwing drill. A closed cut-out requires the use of a radial tightening tool, for example a spanner or an angular Allen key.

The locking element may include a coupling body. The coupling body may be arranged to absorb both an axial force and a radial force. The coupling body may be a body with an outer shape which is complementary to cut-outs in the sleeve and bit ring and thereby lock the sleeve and the bit ring to each other. The coupling body can be locked to the sleeve and the bit ring by means of a press fit, a set screw or another suitable locking device.

The first end portion of the sleeve and the bit ring may include complementary toothings arranged to prevent relative rotation between the sleeve and the bit ring. A toothing as described can transmit a torque from the sleeve to the bit ring during drilling, and thereby reduce the forces applied to the fastening means. This is particularly advantageous if the bit ring is attached to the sleeve with screws arranged axially, wherein a toothing may reduce or eliminate the shear forces on the screws.

The bit ring may include several detachable teeth. The effect of detachable teeth is that teeth that are destroyed may be replaced, while the rest of the teeth may be kept. If a tooth is destroyed, a first bit ring which includes the destroyed tooth may be replaced with a new, second bit ring. After that, the first bit ring may be repaired while the second bit ring is in use.

In a second aspect, the invention relates to an assembly comprising an annular cutter according to the invention, and a drive unit, the annular cutter being connected to the drive unit. The drive unit is arranged to rotate the annular cutter in at least one direction. The drive unit may be a drilling rig, a drill or some other device arranged to rotate the annular cutter.

EXEMPLARY EMBODIMENTS

In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings. For the sake of order, it is pointed out that FIGS. 1 and 14-19 describe the first aspect of the invention. FIGS. 4-7 and 12-3 show solutions that may be combined with the first aspect of the invention. FIGS. 2-3 and 8-11 show solutions on which the invention has been built, but which are not combinable with the first aspect of the invention:

FIG. 1 shows an annular cutter according to the invention with a first coupling of a bit ring;

FIG. 2 shows the coupling of FIG. 1 on a larger scale;

FIG. 3 shows a section of FIG. 2;

FIG. 4 shows an annular cutter with a second coupling of the bit ring;

FIG. 5 shows a section of the bit ring of FIG. 4 on a larger scale;

FIG. 6 shows the second coupling on a larger scale;

FIG. 7 shows a section of FIG. 6;

FIG. 8 shows a third coupling of the bit ring;

FIG. 9 shows a section of FIG. 8;

FIG. 10 shows a fourth coupling of the bit ring;

FIG. 11 shows a section of FIG. 10;

FIG. 12 shows a fifth coupling of the bit ring;

FIG. 13 shows a section of FIG. 12;

FIG. 14 shows a sixth coupling of the bit ring;

FIG. 15 shows a first section of FIG. 14;

FIG. 16 shows a second section of FIG. 14;

FIG. 17 shows an alternative embodiment of the sixth coupling shown in FIG. 16;

FIG. 18 shows a bit ring as shown in FIG. 14, on a smaller scale; and

FIG. 19 shows a section of FIG. 18 on a larger scale.

FIG. 1 shows an annular cutter 1 according to the invention, the annular cutter 1 being in an operative position in a ground 99. The annular cutter 1 comprises a sleeve 2 and a bit ring 3. The bit ring 3 is detachably attached in a rotationally rigid manner to the sleeve 2 via a first coupling 4 a. The annular cutter comprises a plurality of couplings 4 a. The annular cutter 1 is arranged in a drilling rig 5 comprising a drive unit 51 and a lifting device 52 arranged to raise and lower the annular cutter 1. The couplings 4 are arranged to absorb a force F1 which is greater than the maximum lifting force F2.

FIGS. 2 and 3 show, from the side and in a cross section A-A, respectively, the coupling 4 a. The sleeve 2 is provided with an end face 21 and an internally threaded portion 23. The bit ring 3 is provided with a corresponding end face 31 and a through cut-out 33. A tooth 35 is attached to the bit ring 3. A screw 12 has been passed through the cut-out 33 of the bit ring 3 and screwed to the threaded portion 23. The head diameter 12 d of the screw 12 is smaller than the thickness 3 d of the bit ring, and the height 12 h of the screw is smaller than the height 40 h of the tooth body. Thereby the screw head is protected in a tangential direction during drilling.

FIG. 4 shows an annular cutter 1 with a second coupling 4 b. The sleeve 2 and the bit ring 3 are provided with corresponding toothings 29, 39. The bit ring 3 is detachably attached to the sleeve 2 via the coupling 4 b. The coupling 4 b includes a screw 12 arranged axially, shown in FIGS. 6 and 7.

FIG. 5 shows a cross section, on a larger scale, of the bit ring of FIG. 4. The bit ring 3 is provided with six axial cut-outs 34 and six corresponding radial cut-outs 33. The axial cut-outs 34 are arranged to receive and enclose the screw 12, shown in FIG. 4. The radial cut-outs are arranged to protect the screw 12. The cut-out 33 gives an angle of motion A1 for a tightening tool. A wider cut-out 33 may give a wider angle of motion A2. See FIGS. 6 and 7 for more details.

FIGS. 6 and 7 show, on a larger scale, the second coupling 4 b shown in FIGS. 4 and 5, from the side and in a section C-C, respectively. The cut-out 34 has a size and shape that make it possible to pass the screw 12 through the cut-out 33 and then screw the screw 12 to the sleeve 22 with a tool. The tooth 35 is attached to the sleeve 3.

FIGS. 8 and 9 show a third coupling 4 c, from the side and in a section D-D, respectively. The bit ring 3 is slipped over the sleeve 2 and attached with a countersunk screw 13 arranged radially. The end face 31 of the bit ring 3 is arranged to rest supportingly against the end face 21 of the sleeve 2. The tooth 35 is attached to the sleeve 3.

FIGS. 10 and 11 show a fourth coupling 4 d, from the side and in a section E-E, respectively. In principle, the fourth coupling 4 d is identical to the third coupling 4 c, with the difference that the countersunk screw 13 has been replaced by a clamping sleeve 14. FIGS. 9 and 10 further show a detachable tooth 36, attached to the bit ring with two screws 37.

FIGS. 12 and 13 show a fifth coupling 4 e, from the side and in a section F-F, respectively. The fifth coupling 4 e comprises a coupling body 16 which is locked to the sleeve 2 and the bit ring 3 by means of two set screws 15. To prevent relative motion between the sleeve 2 and the bit ring 3, an annular cutter 1 provided with coupling bodies 16 should include at least three coupling bodies 16 evenly spaced along the circumference of the annular cutter 1. The tooth 35 is attached to the sleeve 3.

FIGS. 14-16 show a sixth coupling 4 f, from the side and in a section G-G and in a section H-H, respectively. The sleeve 2 and bit ring 3 are provided with a conical coupling portion 60, in which the bit ring 3 has a protrusion 63 with two converging side faces 64 and the sleeve 2 has a groove 61 with two complementary side faces 62, the protrusion 63 and the groove 61 being arranged to engage with each other.

The conical coupling portion 60 is so formed that an axial clearance 61 is created between the top of the protrusion 63 and the bottom of the groove 61. Thereby a greatest possible contact between the sloping faces 62, 64 is ensured.

When the screw 12 (FIG. 15) is tightened, the surface pressure and thereby the friction between the first and second sloping surfaces 62, 63 will increase.

FIG. 17 shows an alternative embodiment of the conical coupling portion shown in FIGS. 14-16, the protrusion 64 being arranged on the sleeve 2 and the groove 61 being arranged on the bit ring 3.

FIG. 18 shows the bit ring of FIGS. 14-16 in perspective.

FIG. 19 shows a section of FIG. 18.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article “a” or “an” before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage. 

1. An annular cutter arranged to drill in the ground, the annular cutter comprising: a sleeve with a first end portion; and a bit ring, wherein one of the sleeve and the bit ring has a groove with two converging side faces, and the other one of the sleeve and the bit ring has a protrusion with two complementary side faces, and the groove and the protrusion are arranged to engage with each other to create a friction surface between the bit ring and the sleeve; and the bit ring is rotationally rigid and detachably attached to the first end portion of the sleeve via a coupling arranged between the first end portion of the sleeve and the bit ring.
 2. The annular cutter according to claim 1, wherein the protrusion is arranged on the bit ring.
 3. The annular cutter according to claim 1, wherein the coupling is arranged to absorb an axial force which is greater than an axial lifting force necessary for lifting the annular cutter out of the ground, the coupling being placed between the first end portion of the sleeve and the bit ring.
 4. The annular cutter according to claim 1, wherein the coupling comprises fastening means taken from a group comprising screws, clamping sleeves and wedges.
 5. The annular cutter according to claim 1, wherein the fastening means is arranged in a cut-out in the end face of the sleeve.
 6. The annular cutter according to claim 3, wherein the coupling includes a coupling body.
 7. The annular cutter according to claim 1, wherein the first end portion of the sleeve and the bit ring comprises complementary toothings arranged to prevent relative rotation between the sleeve and the bit ring.
 8. The annular cutter according to claim 1, wherein the bit ring includes several detachable teeth.
 9. An assembly comprising an annular cutter and a drive unit, the annular cutter being connected to the drive unit comprising: a sleeve with a first end portion; and a bit ring, wherein one of the sleeve and the bit ring has a groove with two converging side faces, and the other one of the sleeve and the bit ring has a protrusion with two complementary side faces, and the groove and the protrusion are arranged to engage with each other to create a friction surface between the bit ring and the sleeve; and the bit ring is rotationally rigid and detachably attached to the first end portion of the sleeve via a coupling arranged between the first end portion of the sleeve and the bit ring.
 10. The annular cutter according to claim 2, wherein the coupling is arranged to absorb an axial force which is greater than an axial lifting force necessary for lifting the annular cutter out of the ground, the coupling being placed between the first end portion of the sleeve and the bit ring.
 11. The annular cutter according to claim 4, wherein the coupling includes a coupling body.
 12. The annular cutter according to claim 5, wherein the coupling includes a coupling body. 